/* CSS变量定义 - 支持主题切换 */
:root {
    /* 浅色主题 */
    --bg-color: #ffffff;
    --text-color: #333333;
    --primary-color: #007bff;
    --secondary-color: #6c757d;
    --border-color: #e0e0e0;
    --card-bg: #ffffff;
    --shadow: 0 2px 10px rgba(0, 0, 0, 0.1);
    --hover-shadow: 0 4px 20px rgba(0, 0, 0, 0.15);
}

/* 深色主题 */
[data-theme="dark"] {
    --bg-color: #1a1a1a;
    --text-color: #e0e0e0;
    --primary-color: #4dabf7;
    --secondary-color: #adb5bd;
    --border-color: #333333;
    --card-bg: #2d2d2d;
    --shadow: 0 2px 10px rgba(0, 0, 0, 0.3);
    --hover-shadow: 0 4px 20px rgba(0, 0, 0, 0.4);
}

/* 全局样式重置 */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif;
    line-height: 1.6;
    color: var(--text-color);
    background-color: var(--bg-color);
    transition: background-color 0.3s ease, color 0.3s ease;
}

.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 20px;
}

/* 导航栏样式 */
.navbar {
    background-color: var(--bg-color);
    box-shadow: var(--shadow);
    position: fixed;
    top: 0;
    width: 100%;
    z-index: 1000;
    transition: all 0.3s ease;
}

.nav-container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 20px;
    display: flex;
    justify-content: space-between;
    align-items: center;
    height: 70px;
}

.nav-logo h2 {
    color: var(--primary-color);
    font-weight: 700;
}

.nav-menu {
    display: flex;
    list-style: none;
    gap: 2rem;
}

.nav-link {
    color: var(--text-color);
    text-decoration: none;
    font-weight: 500;
    transition: color 0.3s ease;
    padding: 0.5rem 1rem;
    border-radius: 5px;
}

.nav-link:hover {
    color: var(--primary-color);
    background-color: rgba(0, 123, 255, 0.1);
}

.nav-toggle {
    display: none;
    flex-direction: column;
    cursor: pointer;
}

.bar {
    width: 25px;
    height: 3px;
    background-color: var(--text-color);
    margin: 3px 0;
    transition: 0.3s;
}

.theme-toggle {
    background: none;
    border: none;
    color: var(--text-color);
    font-size: 1.2rem;
    cursor: pointer;
    padding: 0.5rem;
    border-radius: 50%;
    transition: background-color 0.3s ease;
}

.theme-toggle:hover {
    background-color: rgba(0, 123, 255, 0.1);
}

/* 主要内容区域 */
.main-content {
    margin-top: 70px;
}

/* 英雄区域 */
.hero {
    background: linear-gradient(135deg, var(--primary-color), #0056b3);
    color: white;
    padding: 100px 0;
    text-align: center;
}

.hero-container {
    max-width: 600px;
    margin: 0 auto;
    padding: 0 20px;
}

.hero h1 {
    font-size: 2.5rem;
    margin-bottom: 1rem;
    font-weight: 700;
}

.hero p {
    font-size: 1.2rem;
    margin-bottom: 2rem;
    opacity: 0.9;
}

.cta-button {
    background-color: white;
    color: var(--primary-color);
    padding: 12px 30px;
    border: none;
    border-radius: 25px;
    font-size: 1.1rem;
    font-weight: 600;
    cursor: pointer;
    transition: transform 0.3s ease, box-shadow 0.3s ease;
}

.cta-button:hover {
    transform: translateY(-2px);
    box-shadow: 0 5px 15px rgba(0, 0, 0, 0.2);
}

/* 卡片区域 */
.cards-section {
    padding: 80px 0;
    background-color: var(--bg-color);
}

.section-title {
    text-align: center;
    font-size: 2.5rem;
    margin-bottom: 3rem;
    color: var(--text-color);
}

.cards-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
    gap: 2rem;
}

.card {
    background-color: var(--card-bg);
    border-radius: 10px;
    padding: 2rem;
    text-align: center;
    box-shadow: var(--shadow);
    transition: transform 0.3s ease, box-shadow 0.3s ease;
}

.card:hover {
    transform: translateY(-5px);
    box-shadow: var(--hover-shadow);
}

.card-icon {
    font-size: 3rem;
    color: var(--primary-color);
    margin-bottom: 1rem;
}

.card h3 {
    font-size: 1.5rem;
    margin-bottom: 1rem;
    color: var(--text-color);
}

.card p {
    color: var(--secondary-color);
    line-height: 1.6;
}

/* 关于区域 */
.about-section {
    padding: 80px 0;
    background-color: var(--card-bg);
}

.about-content {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 3rem;
    align-items: center;
}

.about-text h3 {
    font-size: 2rem;
    margin-bottom: 1rem;
    color: var(--text-color);
}

.about-text p {
    margin-bottom: 1.5rem;
    color: var(--secondary-color);
}

.feature-list {
    list-style: none;
}

.feature-list li {
    padding: 0.5rem 0;
    color: var(--text-color);
}

.feature-list i {
    color: var(--primary-color);
    margin-right: 0.5rem;
}

.about-image {
    text-align: center;
}

.image-placeholder {
    width: 100%;
    height: 300px;
    background-color: var(--border-color);
    border-radius: 10px;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 3rem;
    color: var(--secondary-color);
}

/* 页脚 */
.footer {
    background-color: var(--card-bg);
    color: var(--text-color);
    padding: 60px 0 20px;
    border-top: 1px solid var(--border-color);
}

.footer-content {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: 2rem;
    margin-bottom: 2rem;
}

.footer-section h3,
.footer-section h4 {
    margin-bottom: 1rem;
    color: var(--text-color);
}

.footer-section ul {
    list-style: none;
}

.footer-section ul li {
    margin-bottom: 0.5rem;
}

.footer-section a {
    color: var(--secondary-color);
    text-decoration: none;
    transition: color 0.3s ease;
}

.footer-section a:hover {
    color: var(--primary-color);
}

.social-links {
    display: flex;
    gap: 1rem;
    margin-top: 1rem;
}

.social-links a {
    display: inline-block;
    width: 40px;
    height: 40px;
    background-color: var(--primary-color);
    color: white;
    border-radius: 50%;
    text-align: center;
    line-height: 40px;
    transition: transform 0.3s ease;
}

.social-links a:hover {
    transform: translateY(-2px);
}

.footer-bottom {
    text-align: center;
    padding-top: 2rem;
    border-top: 1px solid var(--border-color);
    color: var(--secondary-color);
}

/* 响应式设计 */
@media screen and (max-width: 768px) {
    .nav-menu {
        position: fixed;
        left: -100%;
        top: 70px;
        flex-direction: column;
        background-color: var(--bg-color);
        width: 100%;
        text-align: center;
        transition: 0.3s;
        box-shadow: var(--shadow);
        padding: 2rem 0;
    }

    .nav-menu.active {
        left: 0;
    }

    .nav-toggle {
        display: flex;
    }

    .hero h1 {
        font-size: 2rem;
    }

    .hero p {
        font-size: 1rem;
    }

    .about-content {
        grid-template-columns: 1fr;
    }

    .cards-grid {
        grid-template-columns: 1fr;
    }

    .footer-content {
        grid-template-columns: 1fr;
        text-align: center;
    }
}

@media screen and (max-width: 480px) {
    .container {
        padding: 0 15px;
    }

    .hero {
        padding: 60px 0;
    }

    .cards-section,
    .about-section {
        padding: 60px 0;
    }

    .section-title {
        font-size: 2rem;
    }
}

/* 平滑滚动 */
html {
    scroll-behavior: smooth;
}

/* 加载动画 */
@keyframes fadeIn {
    from {
        opacity: 0;
        transform: translateY(20px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

.card {
    animation: fadeIn 0.6s ease-out;
}
